The US House select committee investigating the Jan 6 Capitol attack on Thursday voted unanimously to subpoena former president Donald Trump for documents and testimony during a public hearing.

“We must seek the testimony under oath of Jan 6’s central player,” said Committee Vice-Chair Liz Cheney, a Republican.

She said a subpoena for Trump is necessary since several witnesses pleaded their Fifth Amendment right when pressed about their conversations with Trump surrounding the 2020 election and the insurrection.

Cheney said the committee had “sufficient evidence” to answer many of the “critical questions” about the attack and to make criminal referrals to the Justice Department, but she said a “key task” remained hearing from Trump.

If the former Republican president refuses to comply with the subpoena and doesn’t appear, the select committee will decide if it will vote to hold him in criminal contempt of Congress. If it does, it will then go to the full House of Representatives for a vote.

Several former presidents have voluntarily testified before the Congress, but there is no Supreme Court precedent that says whether Congress has the power to compel a former president to testify on his actions in office.

The vote on the motion to subpoena Trump was unanimous, 9-0, with all seven Democrats and two Republicans affirming their yes votes. The hearing concluded after the vote.

“The chance we see him testify is almost zero,” Randall Eliason, a former federal prosecutor in Washington, DC, told The Wall Street Journal. “And even if he does appear, he is likely to assert his right under the Fifth Amendment not to answer questions.”

The issue would be moot if Republicans take back the House after November’s midterm elections as they could cancel the subpoena, Eliason said.

A subpoena would come more than a year since the committee began its investigation.

Thursday’s hearing — the ninth and likely final one — focused on Trump’s state of mind before and after the election. The panel also examined what it has described as “ongoing threats to democracy that persist to this day”, as Trump and some other Republicans continue to claim the 2020 presidential election was stolen.

Representative Bennie Thompson, a Mississippi Democrat and committee chairman, said the committee recognizes that subpoenaing a former president is an extraordinary step, which is why the panel will “take this step in full view of the American people”.

“We want to hear from him,” Thompson said.

“The committee needs to do everything in our power to tell the most complete story possible and provide recommendations to help ensure nothing like Jan 6 ever happens again.”

Thompson said speaking with Trump goes beyond the committee’s “fact-finding” and is a question about accountability to the people. “He is required to answer for his actions,” he said.